Citizen science has advanced science for hundreds of years, contributed to many peer-reviewed articles, and in-formed land management decisions and policies across the United States. Over the last 10 years, citizen science

has grown immensely in the United States and many other countries. Here, we show how citizen science is a

powerful tool for tackling many of the challenges faced in the field of conservation biology. We describe the

and environmental protection. The first path includes building scientific knowledge, while the other path in-volves informing policy and encouraging public action. We explore how citizen science is currently used and de-scribe the investments needed to create a citizen science program. We find that: